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. available oxygen. Fee does not occur naturally in the environment but is a byproduct of reducing environments. Table I represents groundwater chemical results showing TPHg MBTEX and DO. Table 2 represents the field measurements obtained from the wells. MW4 and MW5 values remained below the lower laboratory detection limits for TPHg. MW3 and MW12 results show decreases in TPHg, while those from MW8 remained the same. MWI, MW2, MW6, MW7, MW9, MW10 and MWI 1 had slight increases in TPHg. All well samples, except from MW13, showed slight increases in BTEX. The water sample obtained from MW13, when compared to the sample obtained from Boring 7 (boring from which MW13 was installed) in June 1997, showed dramatic reductions occurring in TPHg, Toluene, Ethylbenzene, and Xylenes with minor reductions in Benzene, see Table 1. A pump blank was obtained and indicates that some cross contamination of samples may have occurred. The wells were sampled in the following order: MW9, MW7, MW6, MW4, MW5, and MWI 1. These wells in the past have all been below laboratory lower detection limits. The following wells which have shown petroleum hydrocarbons in past samplings were then sampled in the following order: MW12, MWS, MW1, MW2, MW13, MW3, and MW10. The pump (Grundfos Redi-Flog) was washed and rinsed after each well. The final rince was sampled and contained the following concentrations TPHg 0.12 mg/L, Benzene 1.6 ug/L, Toluene 12 ug/L, Ethylbenzene 5.5 ug/L, Xylenes 39 ug/L and MTBE <5ug/L. This pump was used instead of LTT vacuum lift pump in order to obtain representative DO samples. . Charts have been developed for MWI, MW2, MW3, MW8, MW10 and MW12 that show the continued decline in concentrations of TPHg in the groundwater and the continued rise of the groundwater elevation since 1991. These charts are located with Table 1. A computer generated averaging trend line demonstrates the decline of gasoline range hydrocarbons in the groundwater for all wells excep for MW12, which is currently showing a slight upward trend. For the most part the MCLS for Benzene, Toluene, Ethylbenzene and Xylenes have not exceeded the primary MCLS for drinking water standards for the State of Calfironia. And the perimeter wells, except MW12, have tested below or at laboratory lower detection limits for TPHg, BTEX and MTBE, showing plume. Of the wells that do test positive for gasoline range hydrocarbons (MWI, MW2, MW3, MW8, MWIO, MW12 and MW13) the following MCLs have not been exceeded with the exception of this latest sampling which contain elevated levels for BTEX due to residuals in the pump. Compound Primary MCL Secondary MCL Benzene 1.0 ug/L none Toluene 150 ug/L 42 ug/L Ethylbenzene 700 ug/L 29 ug/L Xylenes 1750 ug/L 17 ug/L 3 R603 Update##50 12197